Noise generator



Feb. 25, 1947- D. D. GRIEG NQISE GENERATOR- Filed Jan. 50. 1943 MULTI- r/Benrm TPHMSMHI'ER FIL TEE IN VEN TOR. 00mm 0. 6/7/66 Patented Feb. 25, 1947 Donald D. Grieg, Forest Hills, N. Y., assigncr to Federal Telephone and Radio Corporation, Newark, N. J.. a corporation of Delaware Application January 30, 1943, Serial No. 474,064

7 Claims. 1

This invention relates to improvements in noise generators, and more particularly to methods and means for increasing the noise output from a noise generator of the gaseous discharge type,

\An object of this invention is to provide a noise generator of the gaseous discharge type having a greater noise output than similar generators heretofore'in use.

- Another object of this invention is to provide a noise generator of the gaseous discharge tube type in which the saw tooth wave generated by high frequency keying is eliminated and a relatively large amount ,of random noise is produced.

A specific object of this invention is the production of a noise generator of the gaseous discharge tube .type in which random noise is generated -by 9, large random ionic output current. These and other objects and advantages of the present invention will become more apparent from the following description of one embodiment and a modification of my invention, illustrated in the accompanying drawings in which:

Fig. 1 is a block circuit diagram of one form of noise generator in accordance with the present invention; and

, Fig. 2 is a similar block circuit diagram of a modified noise generator system.

In the producton of noise, for example, to be used in jamming systems, it is desirable to produce a large amount of irregular, random noise at audible frequencies. The use of a gaseous discharge type tube for this purpose has already been proposed, but the random noise produced by arrangements heretofore known has been relatively small. By means of the present invention, however, it is possible to produce a relatively large amount of random noise. For this purpose I propose to use a gaseous type discharge tube,

indicated at H] in Fig. 1, whose anode voltage is supplied from a keyed source such as a multivibrator l2. Inaccordance with the present invention the keying rate or frequency is made extremely high as, for example, at 15,000 or 20,000 cycles per second. Ionization and de-ionization of the tube will take place at the multivibrator keyingrate and will generate a high frequency generally saw tooth electron current output which will be above the desired audible frequency. This electron current is indicated by the arrow I I. This high frequency ionization and de-ionization, however, will produce a disproportionally large amount of ionic current, indicated by the arrow 16 which has random components at lower frequencies than the keying from the tube In is then passed through a lowpass filter l8 and amplified by amplifier 20, the transmitter 22 will. transmit nothing but these low frequency random noises. By increasing the keying rate to'such a high value, the amount of low frequency audible noise has shown to increase approximately 38 decibels in voltage of noise output compared to the output ordinarily obtained with constant gas discharge.

Instead of using a multivibrator or similar device to supply a keyed source of anode voltage to the gas discharge tube, the tube may be connected in a relaxation oscillator circuit 24 as indicated in Fig, 2, the constants of the circuit being so chosen that the tube will oscillate at a similar high frequency, Again, the amount of ionic current l6 produced at this high frequency will be extremely large and if the output of the tube is connected through a low-pass filter and an amplifier, the transmitter will transmit these relatively large amounts of random noise, while the high frequency saw tooth of the electron current, not audible at frequency chosen will have been eliminated by the filter.

While the invention has been illustrated in connection with certain specific apparatus, it will be clear to all those skilled in this art that other equivalent arts may be used, for example, while I have indicated a multivibrator in Fig. 1 to supply high frequency keying voltage to the anode of the tube, other suitable and comparable means may be used. Instead of using a low-pass filter to eliminate the undesired high frequency electron currents, this filter might be embodied and form part of some suitable coupling stage, Accordingly, while I have described above the principles of my invention in connection with certain specific apparatus and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of my invention as set forth in the objects and the accompany ing claims.

I claim:

1. In a noise generator, a gaseous discharge tube, a source of anode potential greater than the break-down potential of said tube, circuit means for connecting said source to said tube including means for starting and stopping the discharge of said tube at a predetermined frequency, and filter means connected to the output of said tube, said filter being so dimensioned as to eliminate the electron current output of said tube while permitting passage or the lower frequency ionic current output.

2. The combination according to claim 1, in which said source and'kstarting and stopping means is amultivibrator.

3. A noise generator including in combination, a. circuit producing electronic currents of only one frequencyand random ionic currents of-audible frequency comprising a gaseous discharge tube, a source of anode potential greater than the break-down potential of said tube connected to 7 said tube comprising a multivibrator keyed to a predetermined high frequency, and an output circuit connected to said tube, and a low-pass filter dimensioned to block the electron current tube output of the keying frequency impressed bythe multivibrator, but permitting the flow of lower frequency ionic currents.

4. The combination according to claim 3, in which the keying frequency of the multiyibrator is above a desired audiblenoisefrediiency, whereby the ionic current frequency will be within the desiredaudible range. V

5. A noise generator including in combination a. gaseous discharge tube, means connected to said tube for continuously keying said tube at only one frequency and forming therewith a relaxation oscillator operating at a predetermined high irequency, and an output circuitconnectedto said tube, including a low-pass filter dimensioned to block the electron current tube output, but permitting the flow of lower frequency ionic currents.

6. The combination. according to claim 5, in

which said means is so dimensioned that said high frequency is above a desired audible noise frequency, whereby the ionic current frequency will be within the desired audible range.

'7. In a noise generator, a gaseous discharge tube, a source of anode potential greater than the break-down potential of said tube, circuit means for connecting said source to said tube including means for starting and stopping the discharge of said tube at a predetermined frequency above a desired audio'noise frequency, so that the ionic current output will fall within the desired audio frequency range, and filter means connected to the output of said tube, said fllter being so dimensioned as to eliminate the electron current output of said tube while permitting passage of the lower frequency ionic current output.

DONALD D. GRIEG.

REFERENCES crrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,957,269 I-Iund May 1. 1934 2,165,509 Ring July 11, 1939 2,173,180 Peterson Sept; 19,1939 2,344,633 Pfieger Mar. 21, 1944 OTHER REFERENCES Pr. Phys. Soc., vol. 34, 1921-22, page 175. (Copy in Library 250-36-13.) 

